Wind tunnel performance of four energy efficient propellers designed for Mach 0.8 cruise

Several advanced aerodynamic and acoustic concepts were investigated in recent wind tunnel tests performed in the NASA-Lewis Research Center 8x6 foot wind tunnel. These concepts included aerodynamically integrated propeller/nacelles, area-ruling, blade sweep, reduced blade thickness, and power (disk) loadings several times higher than conventional designs. Four eight-bladed propeller models were tested to determine aerodynamic performance. Relative noise measurements were made on three of the models at cruise conditions. Three of the models were designed with swept blades and one with straight blades. At the design Mach number of 0.8, power coefficient of 1.7, and advance ratio of 3.06, the straight bladed model had the lowest net efficiency of 75.8 percent. Increasing the sweep to 30 deg improved the performance to near 77 percent. Installation of an area-ruled spinner on a 30 deg sweep model further improved the efficiency to about 78 percent. The model with the highest blade sweep (45 deg) and an area-ruled spinner had the highest net efficiency of 78.7 percent, and at lower power loadings the efficiency exceeded 80 percent. At lower Mach numbers the 30 deg swept model had the highest efficiency. Values near 81 percent were obtained for the design loading at speeds to Mach 0.7. Relative noise measurements indicated that the acoustically designed 45 deg sweep model reduced the near field cruise noise by between 5 and 6 dB

Design and performance of energy efficient propellers for Mach 0.8 cruise

The increased emphasis on fuel conservation in the world has stimulated a series of studies of both conventional and unconventional propulsion systems for commercial aircraft. Preliminary results from these studies indicate that a fuel saving of 14 to 40 percent may be realized by the use of an advanced high-speed turboprop. This turboprop must be capable of high efficiency at Mach 0.8 cruise above 9.144 km altitude if it is to compete with turbofan powered commercial aircraft. Several advanced aerodynamic concepts were investigated in recent wind tunnel tests under NASA sponsorship on two propeller models. These concepts included aerodynamically integrated propeller/nacelles, area ruling, blade sweep, reduced blade thickness and power (disk) loadings several times higher than conventional designs. The aerodynamic design methodology for these models is discussed. In addition, some of the preliminary test results are presented which indicate that propeller net efficiencies near 80 percent were obtained for high disk loading propellers operating at Mach 0.8

High real-space resolution measurement of the local structure of Ga_1-xIn_xAs using x-ray diffraction

High real-space resolution atomic pair distribution functions (PDF)s from the alloy series Ga_1-xIn_xAs have been obtained using high-energy x-ray diffraction. The first peak in the PDF is resolved as a doublet due to the presence of two nearest neighbor bond lengths, Ga-As and In-As, as previously observed using XAFS. The widths of nearest, and higher, neighbor pairs are analyzed by separating the strain broadening from the thermal motion. The strain broadening is five times larger for distant atomic neighbors as compared to nearest neighbors. The results are in agreement with model calculations.Comment: 4 pages, 5 figure

Local structure study of In_xGa_(1-x)As semiconductor alloys using High Energy Synchrotron X-ray Diffraction

Nearest and higher neighbor distances as well as bond length distributions (static and thermal) of the In_xGa_(1-x)As (0<x<1) semiconductor alloys have been obtained from high real-space resolution atomic pair distribution functions (PDFs). Using this structural information, we modeled the local atomic displacements in In_xGa_(1-x)As alloys. From a supercell model based on the Kirkwood potential, we obtained 3-D As and (In,Ga) ensemble averaged probability distributions. This clearly shows that As atom displacements are highly directional and can be represented as a combination of and displacements. Examination of the Kirkwood model indicates that the standard deviation (sigma) of the static disorder on the (In,Ga) sublattice is around 60% of the value on the As sublattice and the (In,Ga) atomic displacements are much more isotropic than those on the As sublattice. The single crystal diffuse scattering calculated from the Kirkwood model shows that atomic displacements are most strongly correlated along directions.Comment: 10 pages, 12 figure

Heterostructures for High Performance Devices

Contains table of contents for Part I, table of contents for Section 1, an introduction, reports on sixteen research projects and a list of publications.DARPA/NCIPTJoint Services Electronics Program Contract DAAL03-92-C-0001National Science FoundationToshiba Corporation Ltd.Charles S. Draper LaboratoriesHertz Foundation FellowshipVitesse SemiconductorGTE LaboratoriesNational Science Foundation FellowshipDARPA/MOSISTexas Instruments, Inc.U.S. Army Research Office Grant DAAL03-92-G-025

Heterostructures for High Performance Devices

Contains table of contents for Part I, table of contents for Section 1, an introduction, reports on eighteen research projects and a list of publications.Charles S. Draper Laboratories Contract DL-H-418483DARPA/NCIPTJoint Services Electronics Program Contract DAAL03-89-C-0001Joint Services Electronics Program Contract DAAL03-92-C-0001IBM Corporation FellowshipNational Science Foundation FellowshipVitesse SemiconductorGTE LaboratoriesCharles S. Draper LaboratoriesElectronics and Telecommunications Research Institute (ETRI) FellowshipNational Science Foundation/Northeastern UniversityTRW SystemsU.S. Army Research OfficeNational Science FoundationAT&T Bell Laboratories FellowshipNational Science Foundation Grant ECS 90-0774

Emissões públicas de ações, volatilidade e insider information na Bovespa

O trabalho utiliza um estudo de evento para examinar os retornos de ações relacionados a emissões públicas por empresas brasileiras listadas na BOVESPA, realizadas entre 1992 e 2002, buscando determinar como o mercado reagiu antes, durante e depois da data do anúncio da emissão. Após utilizar a metodologia convencional de mensuração de retornos anormais por OLS, foram utilizados modelos ARCH e GARCH, que levam em consideração a heteroscedasticidade condicional da volatilidade dos retornos anormais, em mais de 70% da amostra, após a constatação da presença desses processos nos resíduos originais. Os resultados mostram que 1) há evidências de insider information antes da data do anúncio, (2) que ocorrem retornos anormais negativos na data do anúncio e (3) que, no período de um ano após as emissões, as ações das empresas que captaram recursos via underwriting tiveram retornos negativos após ajuste ao risco e ao mercado

Cancer survivors' experiences of using survivorship care plans: a systematic review of qualitative studies

Purpose: Cancer survivorship care plans (SCPs) are currently used in care settings to assist survivors during the transition from treatment to survivorship. In this paper, the experiences of cancer survivors are examined to provide their perspective of how survivorship care plans are used in practice. Methods: A systematic review and critical review of the qualitative literature regarding the experiences of cancer survivors using survivorship care plans was completed. Databases reviewed included CINAHL, AMED, Embase, MEDLINE, Informit, ProQuest, PsycINFO, ScienceDirect, Wiley Online Library, Scopus and Web of Science from 2000 to 2014.ResultsEleven qualitative studies were appraised for methodological quality and content. They revealed four key themes: stakeholders agreed that SCPs should be used as a key strategy for cancer survivors; there was a lack of consensus on the format, content and who should develop the SCP; cancer survivors do not consistently receive SCPs; and there was a lack of evidence to support the use of SCPs in practice. Conclusions: There is great potential for SCPs to assist cancer survivors and this is supported by the range of qualitative literature examined in this study. Further research is required to examine the many practical issues relating to the delivery of SCPs and how they may be used across a variety of care contexts as well as providing further evidence to support their use. Implications for Cancer Survivors: With further research, refinement and contributions made by survivors, health researchers and health care professionals, the survivorship care plan is proposed to be a useful and practical tool aimed at supporting the survivorship continuum of care